QUIC Transport Protocol

RFC 9000 defines QUIC, a secure, general-purpose, multiplexed transport protocol operating directly on top of UDP.

Core Features

• Authenticated & Encrypted: All packet headers and payloads are encrypted using TLS 1.3 (RFC 9001). Middleboxes and firewalls cannot inspect or tamper with stream headers.
• Stream Multiplexing: Supports arbitrary numbers of concurrent unidirectional and bidirectional streams.
• Low Latency Handshake: 1-RTT connection setup for new connections, and 0-RTT early-data connection resumption with pre-shared keys (PSK) and bounded anti-replay protection.
• Congestion Control: NewReno controller plus RTT/loss detection primitives (loss.zig, cc.zig); ACK tracking is integrated into the receive path.

QUIC Packet Types

• Initial: Initiates connection and carries TLS ClientHello / ServerHello.
• Handshake: Completes mutual authentication and exchanges application keys.
• 0-RTT Protected: Carries early application data for resumed sessions.
• 1-RTT (Short Header): Carries standard application streams with minimum 1-byte header overhead.

Related

• Protocol: HTTP/3
• Protocol: UDP
• Example: HTTP/3 QUIC